Are there ways to learn and practice Deep Learning without downloading and installing anything?
As I understand, I think you wish to directly try out some deep learning stuff and things like library downloading, tools downloading, and managing all these really stop you from even starting to try out deep learning experiments.If this is what you asked for:


Google Colab

I think this is the best place for you.
Anyone with a Google Drive account can sign up for Colab by heading to 
 and following the listed instructions.

Since you mentioned that you just wanted to try out and practice stuffs, this would be 
ideal for you.


All major Python libraries like TensorFlow, Scikit-learn, Matplotlib among many 
others 
are pre-installed and ready to be imported.
Built on top of Jupyter Notebook


Please have a quick look at:

https://medium.com/lean-in-women-in-tech-india/google-colab-the-beginners-guide-5ad3b417dfa


2.Microsoft Azure

The Azure free account is available to all new customers of Azure. If you have never 
  tried or paid for Azure before, you’re eligible.
  Try out a student account:
   https://azure.microsoft.com/en-in/free/students/

Hope this helps, go ahead with practicing deep learning 
if not please feel free to raise questions, always ready to help